1. Field of the Invention
The subject invention relates to storage stable dispersions comprising certain aromatic polyesters dispersed in certain polyhydroxyl compounds and their process of preparation. The dispersions are useful for the preparation of polymers containing urethane and/or isocyanurate linkages.
2. Description of the Prior Art
Dispersions of fillers in polyhydroxyl compounds which are preferably used for the preparation of reinforced polyurethane foams are disclosed in numerous patents and patent applications.
According to the disclosure in European published application No. 11,752, (U.S. Pat. No. 4,243,755) stable filler-polyol dispersions are prepared by simultaneously reducing the particle size of organic and inorganic fillers to no less than 7 microns and dispersing the filler in polyols by means of high local energy density.
Dispersions of copolymers, preferably styreneacrylonitrile copolymers in hydroxyl group containing polyethers, are also known. See, for instance, German Pat. No. 1,222,669, (U.S. Pat. Nos. 3,304,273, 3,383,351 and 3,523,093), German Pat. No. 1,152,536 (British Pat. No. 1,040,452), and German Pat. No. 1,152,537 (British Pat. No. 987,618). Moreover, if the vinyl monomers are directly copolymerized in the polyether polyols, the resultant particles are generally so small that there is no tendency toward sedimentation. A problem with these dispersions, however, is that they must be free of monomers in order to result in polyurethane foams which are odor-free and toxicologically unobjectionable. Otherwise, they cannot be used in the typical areas of application, for instance, in automobile seats and upholstered furniture. This requires, however, that the monomers must be separated from the dispersions, for instance, with the aid of thin-film evaporators.
Also known are dispersions of polyisocyanatepolyaddition products, particularly polyhydrazodicarbonamides and polyhydroxyl compounds [German Application No. 1,260,142 (U.S. Pat. No. 3,325,421), German Published Application No. 2,513,816 (U.S. Pat. No. 4,042,537)] and dispersions of high melting polyesters and polyhydroxyl compounds [European Published Application No. 17,111]. Dispersions of the above-referenced type which contain fillers are usually obtained by the in situ preparation of a dispersed phase in a polyhydroxyl compound. A problem with these relatively stable dispersions is that their preparation is very difficult to reproduce. If the dispersions begin to precipitate during preparation or storage, (for instance because of slight processing variations, temperature variations, or as a result of an external generally unknown trigger event), the fillers can generally no longer be dispersed.
According to European Published Application No. 17,111, dispersions are produced by melting by means of a high shear gradient. It is characteristic of this process that the disperse phase is not bonded into the polymer structure during the polyurethane manufacture, but that it is present in the molded part as a reinforcing filler. It is also characteristic of the process that the temperature during the polyurethane reaction is chosen in such a manner that the melting point of the crystals is not reached.
Storage stable crystalline suspensions used for the manufacture of urethane and/or isocyanurate group-containing foams are described in German Patent Application No. P 3,001,462.1. The crystalline suspensions contain polyols generally used in preparing flexible foams as the continuous phase and rigid crystalline organic compounds having at least one Zerewitinoff active hydrogen atom, which have melting points of 30.degree. C. to 260.degree. C. and molecular weights of 178 to approximately 100,000, as the disperse phase. These dispersions are advantageous because the rigid crystalline organic compound can be incorporated in the polyurethane structure in a controllable manner by its melting point and/or the transition from the disperse into the continuous phase. Thereby the already formed cell membranes can be further stabilized. The problem with these dispersions, however, is that the crystalline suspensions are difficult to reproduce.
In view of the problems described in the prior art, there is a need for storage stable dispersions which are flowable at room temperature and which can be produced in an easily reproducible manner. Furthermore, the dispersions must be capable of reacting to form polymers containing urethane and/or isocyanurate linkages by using common processing machinery.